The present invention relates to variable displacement compressors that are used, for example, in vehicle air conditioners.
Examples of the variable displacement compressors are disclosed in Japanese unexamined patent publication No. 8-311634 and No. 9-60587. A housing of the respective variable displacement compressor defines cylinder bores, each of which receives a piston. The housing rotatably supports a drive shaft, and a rotor is fixed to the drive shaft. Furthermore, a pivotal swash plate, which is connected to the piston, engages and is guided by the drive shaft. The swash plate is often made of aluminum or aluminum alloy material to reduce the weight of the compressor. A hinge mechanism connects the rotor to the swash plate. The swash plate is rotated integrally with the drive shaft through the rotor and the hinge mechanism. The hinge mechanism permits pivotal motion and sliding motion of the swash plate.
The hinge mechanism includes a first hinge part, which extends from the swash plate, and a second hinge part, which extends from the rotor. The hinge mechanism further includes a pair of guide pins. A base end of each guide pin is press fitted into a corresponding mounting hole of the first hinge part. A distal end of each guide pin is slidably received in a corresponding guide hole of the second hinge part. When the swash plate is moved in an axial direction of the drive shaft, the distal end of each guide pin slides in the corresponding guide hole to guide the motion of the swash plate.
Rotation of the drive shaft is converted to reciprocation of each piston through the rotor, the hinge mechanism and the swash plate. During the back stroke of the piston, from top dead center to bottom dead center, the refrigerant gas is drawn into the cylinder bore. Then, during the forward stroke of the piston, from bottom dead center to top dead center, the refrigerant gas is compressed in the cylinder bore and, then, is discharged from the cylinder bore. The displacement of the variable displacement compressor can be adjusted by changing the inclination of the swash plate to change the stroke of the piston.
In the prior art, the first hinge part is integrally formed with the swash plate. That is, the first hinge part is also made of aluminum or aluminum alloy material. Therefore, in comparison to first hinge parts that are integrally formed with an iron-based swash plate, an aluminum-based first hinge part is less rigid. As a result, it is difficult to form an aluminum-based first hinge part that has satisfactory strength. Furthermore, it is difficult to press fit the base end of the guide pin into the mounting hole of an aluminum-based first hinge part in a manner that assures satisfactory strength.
Therefore, when an iron-based swash plate is replaced with an aluminum-based swash plate for reducing the weight of the compressor, the strength and durability of the hinge mechanism are reduced.